Foot Pathology
Early Complications of General Trauma
Visceral Fractures
These involve damage to internal organs.
Example: High-impact trauma to the torso resulting in broken ribs which subsequently puncture a lung.
Vascular Fractures
These involve damage to blood vessels.
Example: Damage to the radial artery from a humerus or elbow fracture.
Example: Damage to the popliteal artery from fractures occurring around the knee.
Compartment Syndrome
Mechanism: Crush injuries lead to extensive swelling and inflammation, which increases pressure within a muscle compartment. Because the fascia cannot expand, this pressure compresses nerves and blood vessels.
Consequences: Severe pain, ischemia, and necrosis.
Risk Factors: High risk in the extremities due to significant muscle mass and non-elastic fascia.
Clinical Indicators (The "5 Ps"):
Pain
Paraesthesia
Paralysis
Pallor
Pulselessness
Management: This is considered an orthopaedic emergency; decompression procedures must be initiated immediately.
Infections
Examples include tetanus or osteomyelitis.
These are particularly associated with compound fractures or surgical interventions.
Haemarthrosis
This is defined as bleeding into the joint space.
It increases the likelihood of joint destruction and later degeneration.
Fat Emboli
This condition is observed more frequently in fractures of the pelvis and long bones.
Mechanism: Fatty marrow escapes into the venous circulation, leading to a lung embolism.
Phalangeal and Metatarsal Fractures
Phalangeal Fractures
Crush Fracture: Often caused by dropping a heavy object on the toes. It frequently results in a comminuted phalanx, with the distal phalanx being the most common site.
Bedroom Fracture: Caused by a direct blow to the toe, such as striking an object like a bedpost. It most commonly affects the 4th and 5th toes, specifically the 5th proximal phalanx.
Metatarsal Fractures: Jones Fracture
Location: Occurs near the base of the 5th metatarsal, specifically within distal to the tuberosity of the 5th metatarsal.
Risk: Carries a high risk of complications due to a poor blood supply and being in a high-stress location.
Differential: It should not be confused with the more common avulsion fracture of the 5th metatarsal styloid.
Metatarsal Fractures: Lisfranc Fracture-Dislocation
Anatomy: Involves the tarsometatarsal joints, typically involving the 2nd metatarsal being displaced from its articulation with the medial cuneiform.
Types of Dislocation:
Homolateral: All metatarsals are displaced in the same direction, usually laterally.
Divergent: The 1st metatarsal is displaced medially, while the others are displaced laterally.
Isolated: One or two metatarsals are dislocated dorsally.
Clinical Presentation: Often accompanied by bruising on the foot.
Tarsal Fractures: Talus and Calcaneus
Talus Neck Fractures
Avulsion of the Anterior Surface: This is the most frequent type, caused by forced plantar flexion.
Vertical Fracture (Aviator’s Fracture): This is the next most common type. It is caused by the downward force of the anterior tibial lip into the talar neck during dorsiflexion.
Complication: Avascular necrosis (AVN), which usually involves the body of the talus.
Calcaneus Fractures
Mechanism: Typically results from a fall from a height; it is also a common site for stress fractures.
Intra-articular Fractures: Involve the subtalar joint. A common complication for these is arthritis.
Extra-articular Fractures: Involve the posterior tuberosity, the anterior process, or the body of the calcaneus.
Outcomes: Severity ranges; while surgery may or may not be required, these can lead to chronic pain and restricted motion.
Gout: Definition, Incidence, and Etiology
Definition: Gout is a metabolic arthritis where monosodium urate crystals or uric acid crystals are found within the joint cavity.
Incidence and Demographics
Gout is more common in males than in females.
Typically occurs over the age of , with peak incidence in the fourth and fifth decades.
Family history is a frequent factor.
Maori and Polynesian communities are genetically predisposed to the condition.
Etiology (Hyperuricaemia)
Hyperuricaemia is an increase in serum urate concentration that leads to monosodium urate crystal deposition.
Causes of Hyperuricaemia:
Over-production of uric acid.
Under-excretion of uric acid.
A combination of over-production and under-excretion.
Classification
Primary Gout: A genetic defect in the enzymatic metabolism of uric acid. This is the most common form.
Secondary Gout: Results from a disease or medication.
Pathogenesis of Gout and Tophi Development
Development of an Acute Attack
A sudden rise in serum urate levels causes the urate to become insoluble and precipitate.
Monosodium urate crystals are deposited within the joint, triggering inflammation.
Crystals are released into various structures, including the synovium, synovial fluid, cartilage, joint capsule, subchondral bone, and periarticular soft tissues.
Cellular Response
Leukocytes (White Blood Cells) attempt to phagocytose the crystals.
This leads to leukocyte death, which triggers a further inflammatory response.
This cycle eventually leads to the destruction of bone and cartilage cells.
Tophi
Characteristics: Hard nodules with irregular surfaces containing deposits of monosodium urate crystals. They increase the inflammatory response.
Timing: They typically do not appear until years or more after the initial attack of gout.
Common Locations:
Synovium and synovial fluid
Subchondral bone
Joint capsule
Periarticular soft tissue
Olecranon bursa
Achilles tendon
Extensor surfaces of the forearm
Chronic Tophaceous Gout: Characterized by more frequent and prolonged attacks that are polyarticular (affecting multiple joints).
Clinical Manifestations and Radiographic Features of Gout
Acute Attack Manifestations
Presentation: Typically monoarticular, most often affecting the big toe.
Onset: Abrupt onset of pain, redness, and swelling, usually beginning at night.
Precipitants: Certain medications, increased exercise, specific foods, alcohol, or dieting.
Duration: Symptoms may last from days to weeks.
Intercritical Period: After the initial attack, the patient is asymptomatic with no joint abnormalities. It may be months or years before the next attack.
Radiographic Features
Soft Tissue Changes: Tophi appear as localized increases in soft tissue density.
Joint Space: The joint space is preserved until late stages of the disease.
Bone Density: There is no general loss of bone density.
Secondary Osteoarthritis: Features of OA may appear in the late stages of gout.
Bone Erosions:
Marginal Erosions: Occur in the "bare area" inside the joint.
Peri-articular Erosions: Found distal to the joint due to pressure from tophi.
Intra-osseous Erosions: Punched-out radiolucent lesions in the subchondral bone.
Rat-bite Sign: Sharply marginated, overhanging bony erosions. These well-demarcated marginal erosions are often found on the first metatarsal head. They are cyst-like lesions with thin sclerotic margins and characteristic overhanging edges.